Composite structure with waste plastic core and method of making same

ABSTRACT

A low cost, lightweight, high strength, long lasting, crack resistant, monolithically formed composite structural material and the method of making the same in which the composite consists of a core constructed from lightweight, granulated scrap or waste plastic bonded together with a cementitious slurry binder. The core is covered on one or more of its sides with a high strength outer layer constructed of layers of non-woven fabric material impregnated with the same cementitous slurry binder with the fibers in the layers of non-woven fabric material forming a three-dimensional reinforcement matrix for the cementitous slurry. The composite of the core and covering is co-formed and cured monolithically with the cementitious slurry being continuous throughout the fibers of the layers of non-woven fabric and the core with the lightweight scrap or waste plastic serving as an aggregate for the core. The composite structural material can be molded or formed in various shapes and configurations for various purposes.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention generally relates to a composite structuralmaterial and the method of making the same and more specifically theinvention relates to a low cost, lightweight, high strength, longlasting, crack resistant, monolithically formed composite structuralmaterial and the method of making the same in which the compositeconsists of a core constructed from lightweight, granulated scrap orwaste plastic bonded together with a cementitious slurry binder. Thecore is covered on one or more of its surfaces with a high strengthouter layer constructed of layers of non-woven fabric materialimpregnated with the same cementitous slurry binder with the fibers inthe layers of non-woven fabric material forming a three-dimensionalreinforcement matrix for the cementitous slurry. The composite of thecore and outer layer are co-formed and cured monolithically with thecementitious slurry being continuous throughout the fibers of the layersof non-woven fabric and the core with the lightweight scrap or wasteplastic serving as an aggregate for the core. The composite structuralmaterial can be molded or formed in various shapes and configurationsfor various purposes.

2. Description of the Prior Art

Various types of composite structural materials are well known and havebeen utilized for various purposes in forming a desired structuralentity. Composite structural materials are frequently formed into panelswhich include a lightweight core material surrounded by or partiallysurrounded by an outer layer of high strength material. The core usuallyprovides lightweight characteristics and insulating properties and theouter layer provides strength, durability, fire resistance and in someinstances, appearance characteristics. Various procedures have beendeveloped for forming the core and applying an outer skin, layer orcoating of various material to the pre-formed core.

Prior U.S. Pat. No. 4,505,449 issued Mar. 19, 1985 and commonly ownedwith the present invention discloses a base having a lightweight foamcore and a coating of cementitous material covering portions of thecore. U.S. Pat. No. 4,303,722 discloses a panel constructed by bondinginorganic fiber webs to a pre-formed foam panel utilizing a mixture ofthermosetting polymer and gypsum. U.S. Pat. No. 4,559,263 discloses theconcept of binding a layer of concrete to a pre-formed board of foamedplastic resin to form a roofing panel. U.S. Pat. No. 4,617,219 disclosesa reinforced cement structure utilizing non-woven fabric reinforcingmaterial encapsulated in a cementitous composition. U.S. Pat. No.4,778,718 discloses a panel having a cementitious matrix reinforced witha three-dimensional fabric distributed uniformly throughout thethickness of the panel. U.S. Pat. No. 4,894,270 discloses a foldedstructure of polymer fabric reinforced cementitious materials. U.S. Pat.No. 4,963,408 discloses a panel in which a pre-formed core isencapsulated with an outer layer consisting of a polymer and loadbearing reinforcing filaments.

The above patents and the prior art cited in those patents and thefollowing U.S. patents are relevant to this invention.

U.S. Pat. No. 4,050,659

U.S. Pat. No. 4,056,251

U.S. Pat. No. 4,305,508

U.S. Pat. No. 4,436,274

U.S. Pat. No. 4,714,715

U.S. Pat. No. 4,764,238

U.S. Pat. No. 4,876,151

While the above prior patents disclose various composite structures theydo not disclose the specific arrangement of a core formed of scrap orwaste plastic and a cementitious slurry binder together with an outercover formed of layers of non-woven fabric material and a cementitiousslurry which is the same slurry as used as a binder for the core withthe components of the composite being co-formed and monolithicallyformed and cured.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a composite structuralmaterial and a method of its manufacture to provide a high strength,lightweight and low cost structural material having high ductility andtoughness with the composite structural material consisting of a corematerial and an outer layer on one or more surfaces of the core.

Another object of the invention is to provide a composite structuralmaterial as set forth in the preceding object in which the core isconstructed of lightweight plastic aggregate in the form of comminutedwaste plastic material such as industrial and post-consumer wasteexpanded polystyrene combined with a cementitious slurry and the outerlayer is in the form of a fibrous reinforcement constructed of anon-woven web of fibrous material such as polypropelene fibers with afiber volume loading of 3-20%. The core material is an ultra-lightweightconcrete made with cementitious slurry binder and lightweight granularplastic as an aggregate. The core and outer layer or layers are madewith the same cementitious slurry and are co-formed and curedmonolithically to create the composite structural material.

A further object of the invention is to provide a composite structuralmaterial in accordance with the preceding objects which effectivelyfulfills the requirements of high strength and toughness/ductility,lightweight, low permeability, insulative ability, fire resistance, lowcost and provided with a long life expectancy.

These together with other objects and advantage which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a panel or pad utilizing the compositestructural material of the present invention.

FIG. 2 is a sectional view, on an enlarged scale, illustrating thespecific arrangement of the components forming the composite structuralmaterial of this invention.

FIG. 3 is a fragmental sectional view, on a scale larger than FIG. 2,illustrating the relationship of the aggregate and the core, the fibersof the cover and the slurry binder.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to the drawings, a composite structuralcomponent in the form of a panel or pad is illustrated in FIG. 1 andgenerally designated by reference numeral 10 and which includes a coregenerally designated by reference numeral 12 and an outer layergenerally designated by reference numeral 14 which may extend over onesurface of the panel, both opposed surfaces or around all of the edgesand all of the surfaces. The core 12 may include passageways, conduit,piping, wiring or the like incorporated therein as indicated byreference numeral 16. Opposed edges may be provided with connecting andaligning members such as a tongue 18 and groove 20 which may be on onlytwo opposite sides or on all four sides. The outer covers or layers 14form the interior and exterior surfaces of the panel and they can betextured or colored when being formed or finished with various materialssuch as plastic, sheathing, painting, grooving or the like forappearance purposes to enable any desired architectural finishcharacteristics to be obtained.

As illustrated in FIG. 2 as well as FIG. 3, the core is constructed ofgranulated or comminuted waste plastic material such as expandedpolystyrene which constitutes the aggregate in the core with theaggregate having a cementitious slurry binder 24 intimately surroundingand interconnecting the aggregate into a rigid form when cured.

The outer cover or layer 14 includes a three-dimensional web ofnon-woven fabric 26 which includes non-woven fibers 28 with acementitious slurry binder 30 intimately surrounding and connecting thefibers 28 when the cementitious slurry binder is cured. The cementitiousslurry binder 24 in the core and the cementitious slurry binder 30 inthe outer layer or cover are the same and the core and outer layercomponents are co-formed and monolithically cured with the cured andhardened slurry binders 24 and 30 becoming a monolithic body thusproviding an ultra lightweight core which is reinforced and rigidifiedby the outer layer or layers with the core and layer or layers beingrigidly formed into a monolithic unit.

In one embodiment of the invention, a load bearing wall panel, 8'long×4' wide×21/2" thick, was formed in accordance with the presentinvention. A cement slurry was mixed in a portable mortar mixer with atotal of 250 pounds of cement slurry being formed with the followingratios by weight: 10 parts Portland cement, 5 parts fine sand, 1 partmicrosilica, 4 parts water and 0.1 parts water reducingsuperplasticizer. Four sheets of a non-woven web material in the form ofa needlepunched polypropelene weighing 8 ounces per sq. yd. with a loftof 1/4" were cut into 4'×8' pieces. Two pieces of the non-woven webmaterial were placed in a shallow 10'×5' pan and were saturated with 50pounds of the cement slurry. The pan was vibrated and the slurryscreeded uniformly into the fiber matrix. The slurry saturated pieces ofnon-woven fabric were placed in the bottom of an 8'×4' by 2 1/1" deepmold which had been treated with a suitable form-release agent.

One hundred and fifty pounds of the slurry was mixed with 5 cu. ft. ofexpanded polystyrene beads derived by hammermilling pieces of wasteexpanded polystyrene board to form 6 cu. ft. of an ultra-lightweightconcrete with a density of 25 pounds per cu. ft. Then, 5 cu. ft. of theultra-lightweight core mixture was deposited into the mold on top of theslurry saturated pieces of non-woven fabric forming the outer layer orcover and vibrated and screeded level with the top of the mold. Theother two pieces of non-woven fabric were saturated with the remaining50 pounds of the slurry in a manner identical to the previous non-wovenpieces and this layer of slurry saturated non-woven pieces was placed ontop of the ultra-lightweight in the mold. A 10'×5' flat plate was thenapplied to bear against the top saturated non-woven layer withsufficient force to compress the composite mixture to the 21/2" moldheight. The entire mold was vibrated externally during this compressionto consolidate the ultra-lightweight concrete core and evenly distributethe cement slurry binder throughout both the core and the outer layer orlayers. The flat plate was then removed and the composite material wasleft to cure monolithically in the mold for 24 hours.

After 24 hours, the composite panel was demolded and the resulting8'×4'×21/2" thick panel weighed approximately 7 pounds per sq. ft. Thecore is approximately 13/4" thick and each outer layer is approximately3/8" thick. Test beams were cut from the panel with the test beams being24" in length, 6" wide and 21/2" thick. These test beams were tested forflexural strength after a 28 day curing period by using 3rd pointloading on an 18" span. This flexural strength is approximatelyequivalent to prior art panels when constructed to be 6" thick and weighapproximately 40 pounds per sq. ft. The core is preferably about 4 partsaggregate by 1 part slurry with the slurry including, by weight, 10parts Portland cement, 5 parts fine sand, 1 part microsilica, 21/2 to 6parts water, and 0 to 0.5 super- plasticizer. The fiber volume in theouter covers or layers may range between 3 and 20% and the bead size ofthe expanded polystyrene may range from 1/16" to 1/4" of nominal size.

This arrangement provides a smooth external appearance to the panel andouter layers inasmuch as the engagement of the slurry with the smoothsurfaces of the mold completely encapsulates and conceals the fibersforming the non-woven fabric.

The use of waste expanded polystyrene in making a composite structuralmaterial removes a non-biodegradable material from the environment andprovides a relatively low cost panel, pad or other structural entitywhich can find many uses in building and other arts. The lightweight,low cost, insulative, fire resistant and environmentally advantageousstructure enables the composite material to be used as a supporting baseor pad for various machinery, building panels and the like.

Panels and other structural entities constructed in accordance with thisinvention overcome various problems which exist with respect to existingpanels. Pre-formed foam cores in the prior art are relatively expensiveand frequently are the most costly component of the panel. Also,significant trade-offs are involved with the choice of the materials tobe used in the outer layer of the laminate. Concrete and gypsum used inthe prior art possess relatively low flexural strengths and thus must beeither applied in thicker sections resulting in greater weight or inconjunction with polymers resulting in higher cost. Fabric reinforcedresins and polymers used as outer layers result in higher cost and lessfire resistance than cementitious materials. Also, outer layers bondedto a pre-formed core can have a problem of delamination. Further,separate bonding agents and relatively complicated manufacturing methodswhich usually must be employed to prevent delamination under structuralloading increase the cost of the panels. Panels which are made withconcrete outer layers are prone to cracking and brittle failure behaviorunless reinforced with steel or high tensile strength materials tocontrol crack formation which of course increases the cost of materialsand labor in forming the panel and when steel reinforcement is used, thepanel may be subject to rust and corrosion.

As compared with the prior art, the high strength of the structuralmaterial o panels of the present invention result from the outer layerand the core material being co-formed and monolithically formed andcured to provide a monolithic construction of the composite. The outerlayer possesses the look and durability of ordinary concrete but hassignificantly enhanced flexural strength due to the amount andthree-dimension orientation of the reinforcing fibers. The cement andlightweight aggregate core has a much higher compressive strength thantypical densities of pre-formed foam used in the prior art. Also,inasmuch as the core and outer layer or layers are formed as one unitwith the cementitious slurry binder continuous throughout, there existsno plane of weakness for delamination to occur.

The relatively lightweight of the composite of this invention is due toboth the use of ground or comminuted foam plastic as an aggregate in thecore and the high flexural strength and crack resistance of the outerlayer or layers. The superior properties of the outer layer provide forthe design of thinner sections to achieve the desired strength ascompared to the prior art. Further, the lightweight of the compositeallows panels or sections of the material to be prefabricated in acontrolled environment and economically shipped to remote locations tobe installed.

The structural material or entity of the present invention includes lowpermeability and fire resistance characteristics which are functions ofboth the outer layer and the core material. The outer layer will provideessentially the same fire resistance and water penetration resistance asordinary concrete. Further, the expanded polystyrene in the corematerial is completely surrounded with cement slurry which is anadvantage over the prior art where the pre-formed foam plastic isvulnerable to fire or water which may penetrate the outer layer due tosurface defects or construction techniques.

The composite material or structural entity of this invention has also alow manufacturing cost primarily due to the materials and simpleprocedures used in its manufacture. The entire composite is formed ofnon-woven fiber webs, recycled waste expanded polystyrene, hydrauliccement, water and aggregate admixtures as desired to obtain certaintextures that are formed and cured at the same time as the cementitiousslurry, less labor and simpler equipment and facilities are utilized ascompared to prior art.

The composite of the present invention can be used in many buildingorientations where panels, supporting pads, bases and the like arepresently used. For example, composite wall panels, floor panels forvarious purposes including supporting computer and electronic units,roofing and ceiling panels, noise-abating or sound-attenuating panelsand surfaces, fire resistant insulation, ultra-lightweight concretehaving insulating characteristics, buoyant structural supports orcomponents including floating docks and the like. Many other uses of thecomposite material also exist in which the lightweight, low cost, highstrength, fire resistant, insulative, high toughness and ductilitycharacteristics are beneficial.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and, accordingly, all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:
 1. A composite structural materialcomprising a core constructed of lightweight particles mixed with acementitious slurry binder, an outer layer constructed of the samecementitious slurry binder reinforced with fibers, said core and outerlayer being co-formed and cured monolithically with the samecementitious slurry binder forming a rigid matrix extendingsubstantially continuously throughout the composite material to form alightweight, low cost, high strength, insulative, fire resistantcomposite material having high toughness and ductility properties. 2.The composite material of claim 1 wherein the lightweight particles inthe core are particles of expanded polystyrene derived by comminutingpost-consumer and industrial waste or scrap expanded polystyrene.
 3. Thecomposite material of claim 2 wherein the expanded polystyrene is in theform of beads having a maximum dimension between 1/16" and 1/4".
 4. Thecomposite material of claim 1 wherein the reinforcing fibers of theouter layer is in the form of a non-woven web.
 5. The composite materialof claim 1 wherein the core has two outer layers co-formed on two sidesof a planar core to form a sandwich panel.
 6. The composite material asdefined in claim 2 wherein the reinforcing fibers of the outer layer isin the form of a non-woven web.
 7. The method of making a compositematerial consisting of the steps of placing at least one layer ofnon-woven web fabric material into a shallow mold, placing acementitious slurry binder containing Portland cement, aggregate waterand admixtures into the mold, vibrating the mold and screeding thebinder to impregnate the non-woven web material with the binder, placinga mixture of waste expanded polystyrene particles and the samecementitious slurry binder into the mold, vibrating and screeding thewaste expanded polystyrene and cementitious slurry binder mixture to alevel with the top edge of the mold to co-form the cementitious slurrybinder, the non-woven web material and expanded polystyrene particlesand placing a plate on the top of the mold to compress the materialstherein and monolithically curing the materials in the mold to form apanel.
 8. The method as defined in claim 7 together the step ofsaturating an additional layer of non-woven web material with the samecementitious slurry binder and placing it across the top of the moldprior to placement of the top plate thereon to form a panel having alayer of non-woven we material and cementitious slurry binder on opposedsurfaces of the composite material.